Hydraulic system

Abstract

A hydraulic system includes a variable displacement first pump, a first linear actuator fluidly connected to the first pump via a first closed-loop circuit, a variable displacement second pump, and second and third linear actuators fluidly connected to the second pump in parallel via a second closed-loop circuit. The system also includes a variable displacement third pump, a fourth linear actuator fluidly connected to the third pump via a third closed-loop circuit, a variable displacement fourth pump, and a first rotary actuator fluidly connected to the fourth pump via a fourth closed-loop circuit. The system further includes a second rotary actuator fluidly connected to the second pump in parallel with the second and third linear actuators. The system also includes a third rotary actuator fluidly connected to the third pump in parallel with the fourth linear actuator.

What is claimed is: 
     
       1. A hydraulic system, comprising:
 a variable displacement first pump; 
 a first linear actuator fluidly connected to the first pump via a first closed-loop circuit; 
 a variable displacement second pump; 
 second and third linear actuators fluidly connected to the second pump in parallel via a second closed-loop circuit; 
 a variable displacement third pump; 
 a fourth linear actuator fluidly connected to the third pump via a third closed-loop circuit; 
 a variable displacement fourth pump; 
 a first rotary actuator fluidly connected to the fourth pump via a fourth closed-loop circuit; 
 a second rotary actuator fluidly connected to the second pump in parallel with the second and third linear actuators; 
 a third rotary actuator fluidly connected to the third pump in parallel with the fourth linear actuator; and 
 a first combining valve configured to selectively combine fluid from the second and third circuits, a second combining valve configured to selectively combine fluid from the first and second circuits, and a third combining valve configured to selectively combine fluid from the third and fourth circuits, wherein the second combining valve is moveable between a flow-passing position and a flow blocking position, the second combining valve directing fluid from the first and second circuits to at least one of the first, second, and third linear actuators and the second rotary actuator in the flow-passing position. 
 
     
     
       2. The system of  claim 1 , further comprising a first switching valve associated with the first linear actuator, a second switching valve associated with the second and third linear actuators, and a third switching valve associated with the second rotary actuator, each of the switching valves being configured to selectively switch a flow direction of fluid passing through the respective actuators. 
     
     
       3. The system of  claim 2 , wherein the second switching valve is configured to reduce a speed of the second and third linear actuators during regeneration of the second and third linear actuators. 
     
     
       4. The system of  claim 2 , wherein the second combining valve is configured to form a combined flow of fluid including fluid from the first and second circuits, during simultaneous operation of the first linear actuator with the second and third linear actuators and the second rotary actuator, in response to a combined demand of the second and third linear actuators and the second rotary actuator exceeding a capacity of the second pump. 
     
     
       5. The system of  claim 4 , wherein the second switching valve is configured to variably restrict passage of the combined flow through the second and third linear actuators, during simultaneous operation of the first linear actuator with the second and third linear actuators and the second rotary actuator. 
     
     
       6. The system of  claim 4 , wherein the first switching valve is configured to selectively switch a flow direction of fluid passing through the first linear actuator independent of a flow direction of the combined flow passing through the second and third actuators, during simultaneous operation of the first linear actuator with the second and third linear actuators and the second rotary actuator. 
     
     
       7. The system of  claim 4 , wherein the third switching valve is configured to selectively switch a flow direction of fluid passing through the second rotary actuator independent of a flow direction of the combined fluid passing through the second and third actuators, during simultaneous operation of the first linear actuator with the second and third linear actuators and the second rotary actuator. 
     
     
       8. A hydraulic system, comprising:
 a variable displacement first pump; 
 a first linear actuator fluidly connected to the first pump via a first closed-loop circuit: 
 a variable displacement second pump; 
 second and third linear actuators fluidly connected to the second pump in parallel via a second closed-loop circuit; 
 a variable displacement third pump; 
 a fourth linear actuator fluidly connected to the third pump via a third closed-loop circuit; 
 a variable displacement fourth pump; 
 a first rotary actuator fluidly connected to the fourth pump via a fourth closed-loop circuit; 
 a second rotary actuator fluidly connected to the second pump in parallel with the second and third linear actuators; 
 a third rotary actuator fluidly connected to the third pump in parallel with the fourth linear actuator; 
 a first combining valve configured to selectively combine fluid from the second and third circuits, a second combining valve configured to selectively combine fluid from the first and second circuits, and a third combining valve configured to selectively combine fluid from the third and fourth circuits; and 
 a first switching valve associated with the first linear actuator, a second switching valve associated with the second and third linear actuators, and a third switching valve associated with the second rotary actuator, each of the switching valves being configured to selectively switch a flow direction of fluid passing through the respective actuators, wherein at least one of the switching valves comprises 
 a variable position four-way valve. 
 
     
     
       9. A hydraulic system, comprising:
 a variable displacement first Pump; 
 a first linear actuator fluidly connected to the first pump via a first closed-loop circuit: 
 a variable displacement second pump; 
 second and third linear actuators fluidly connected to the second pump in parallel via a second closed-loop circuit; 
 a variable displacement third pump; 
 a fourth linear actuator fluidly connected to the third pump via a third closed-loop circuit; 
 a variable displacement fourth pump; 
 a first rotary actuator fluidly connected to the fourth pump via a fourth closed-loop circuit; 
 a second rotary actuator fluidly connected to the second pump in parallel with the second and third linear actuators; 
 a third rotary actuator fluidly connected to the third pump in parallel with the fourth linear actuator; and 
 a first combining valve configured to selectively combine fluid from the second and third circuits, a second combining valve configured to selectively combine fluid from the first and second circuits, and a third combining valve configured to selectively combine fluid from the third and fourth circuits, 
 wherein the first and second combining valves are configured to combine fluid from the first, second, and third circuits, during simultaneous operation of the second, third, and fourth linear actuators, in response to a combined demand of the second and third linear actuators exceeding a combined capacity of the first and second pumps. 
 
     
     
       10. The system of  claim 9 , wherein the third combining valve is configured to combine fluid from the fourth circuit with fluid from the first, second, and third circuits, during simultaneous operation of the second, third, and fourth linear actuators, in response to a combined demand of the second and third actuators exceeding a combined capacity of the first, second, and third pumps. 
     
     
       11. A hydraulic system, comprising:
 a variable displacement first pump; 
 a first hydraulic cylinder associated with a work tool of a machine, the first hydraulic cylinder being fluidly connected to the first pump via a first closed-loop circuit; 
 a variable displacement second pump; 
 second and third hydraulic cylinders associated with a boom of the machine, the second and third hydraulic cylinders being fluidly connected to the second pump in parallel via a second closed-loop circuit; 
 a variable displacement third pump; 
 a fourth hydraulic cylinder associated with a stick of the machine, the fourth hydraulic cylinder being fluidly connected to the third pump via a third closed-loop circuit; 
 a variable displacement fourth pump; 
 a swing motor associated with a body of the machine, the swing motor being fluidly connected to the fourth pump via a fourth closed-loop circuit; 
 a first travel motor associated with a first traction device of the machine, the first travel motor being fluidly connected to the second pump in parallel with the second and third hydraulic cylinders; 
 a second travel motor associated with a second traction device of the machine, the second travel motor being fluidly connected to the third pump in parallel with the fourth hydraulic cylinder; 
 a first combining valve configured to selectively combine fluid from the second and third circuits; 
 a second combining valve configured to selectively combine fluid from the first and second circuits; and 
 a third combining valve configured to selectively combine fluid from the third and fourth circuits, wherein the first hydraulic cylinder is configured to operate simultaneously with at least one of the second and third hydraulic cylinders and the first travel motor while fluid from the first and second circuits is combined by the second combining valve. 
 
     
     
       12. The system of  claim 11 , further comprising a first switching valve associated with the first hydraulic cylinder, a second switching valve associated with the second and third hydraulic cylinders, and a third switching valve associated with the second travel motor, the first, second, and third switching valves being configured to selectively switch a flow direction of fluid passing through the first hydraulic cylinder, the second and third hydraulic cylinders, and the second travel motor, respectively. 
     
     
       13. The system of  claim 12 , wherein during simultaneous operation of the first, second, and third hydraulic cylinders while the machine is stationary, the first combining valve is configured to form a combined flow of fluid, including fluid from the first and second circuits, in response to a combined demand of the second and third hydraulic cylinders exceeding a capacity of the second pump, the second switching valve being configured to restrict passage of the combined flow through the second and third hydraulic cylinders. 
     
     
       14. The system of  claim 13 , wherein the second switching valve is configured to change a speed of the second and third hydraulic cylinders, independent of a speed of the first hydraulic cylinder, while the second switching valve receives the combined flow of fluid. 
     
     
       15. A method of controlling a hydraulic system, comprising:
 providing fluid to a first linear actuator with a variable displacement first pump via a first closed-loop circuit; 
 providing fluid to second and third linear actuators, in parallel, with a variable displacement second pump via a second closed-loop circuit; 
 providing fluid to a fourth linear actuator with a variable displacement third pump via a third closed-loop circuit; 
 providing fluid to a first rotary actuator with a variable displacement fourth pump via a fourth closed-loop circuit; 
 providing fluid to a second rotary actuator, in parallel with the second and third linear actuators, with the second pump; 
 providing fluid to a third rotary actuator, in parallel with the fourth linear actuator, with the third pump; 
 forming a combined flow of fluid in response to a combined demand of the second and third linear actuators exceeding a capacity of the second pump, the combined flow comprising fluid from the second circuit and fluid from at least one of the first, third, and fourth circuits; and 
 directing the combined flow to the second and third linear actuators while providing fluid to the actuator of the at least one of the first, third, and fourth circuits such that the second and third linear actuators operate simultaneously with the actuator of the at least one of the first, third, and fourth circuits. 
 
     
     
       16. The method of  claim 15 , wherein the combined flow comprises fluid from the first, second, and third circuits, the combined flow being formed in response to the combined demand of the second and third linear actuators exceeding a combined capacity of the first and second pumps. 
     
     
       17. The method of  claim 15 , further comprising variably restricting flow of the combined flow through the second and third linear actuators during simultaneous operation of the second and third linear actuators and the actuator of the at least one of the first, third, and fourth circuits. 
     
     
       18. The method of  claim 15 , further comprising changing at least one of a speed and a direction of the second and third linear actuators independent of a speed and a direction of the actuator of the at least one of the first, third, and fourth circuits during simultaneous operation of the second and third linear actuators and the actuator of the at least one of the first, third, and fourth circuits.